Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2013
Publication Date: 2/19/2013
Publication URL: http://handle.nal.usda.gov/10113/56705
Citation: Yang, T., Peng, H., Whitaker, B.D., Jurick II, W.M. 2013. Differential expression of calcium-regulated SlSRs in response to abiotic and biotic stresses in tomato fruit. Physiologia Plantarum. 148(3):445-455.
Interpretive Summary: Nearly a quarter of all fresh produce in the U.S. market is lost after harvest due to spoilage resulting from mechanical wounding, low temperature injury, and microbial decay. The positive effects of calcium on many postharvest maladies are well known, but the molecular mechanisms underlying these effects remain unclear. This study explored roles of members of the calcium-regulated SlSR gene family in responses of tomato fruit to wounding, chilling, and infection by a decay-causing fungus, as well as two hormones that activate defenses against various types of stress. The results showed distinct patterns of gene expression among the seven SlSRs and further indicated that individual SlSRs have unique roles in responses to specific stress signals. This research is aimed at understanding the mechanisms of tomato fruit stress tolerance and decay resistance. Knowledge of genes controlling these mechanisms will help plant geneticists and breeders, and their industry partners, to develop new tomato lines bearing fruit that maintain good quality after storage and shelf life.
Technical Abstract: Calcium has been shown to increase stress tolerance, enhance fruit firmness and reduce decay. Previously we reported that seven tomato SlSRs encode calcium/calmodulin-regulated proteins, and that their expressions are developmentally regulated during fruit development and ripening, and are also responsive to ethylene. To study the roles of this gene family during postharvest handling, tomato fruit at the mature green stage were subjected to chilling and wounding injuries, infected with Botrytis cinerea, and treated with salicylic acid or methyl jasmonate. Gene expression studies indicated that the seven SlSRs differentially respond to different stress signals. SlSR2 was the only gene upregulated by all the treatments. SlSR4 acted as a late pathogen-induced gene; it was upregulated by salicylic acid and methyl jasmonate, but downregulated by cold treatment (chilling). SlSR3L was cold- and wounding-responsive, and was also induced by salicylic acid. SlSR1 and SlSR1L were repressed by cold, wounding, and pathogen infection, but were upregulated by salicylic acid and methyl jasmonate. Overall, results of these expression studies indicate that individual SlSRs have distinct roles in responses to the specific stress signals, and SlSRs may act as a coordinator(s) connecting calcium-mediated signaling with other stress signal transduction pathways during fruit ripening and storage.